08/15/2013 – Extreme events like heat waves, droughts, heavy rain might not only occur more frequently due to climate change. They could also force global warming if terrestrial ecosystems release CO2 as a result of those extremes. An international team of researchers now analyzed the impacts of extremes on forests, bogs, grass landscapes and arable areas througout the world, among them scientists from the Potsdam Institute for Climate Impact Research (PIK). Terrestrial ecosystems absorb about 11 billion tons less carbon dioxide every year as the result of the extreme climate events than they could if the events did not occur, the researchers write in the renowned journal Nature. This is equivalent to approximately a third of global CO2 emissions per year.

„Terrestrial ecosystems are vital for the global carbon cycle and have a buffer effect in the climate system,“ co-author Kirsten Thonicke from PIK says. In the past 50 years, plants and the soil have absorbed up to 30 percent of the CO2 that humans have set free, primarily from fossil fuels. With data from satellites and recording stations the scientists calculated in extensive computer simulations the global effect of extremes on the carbon balance. One example of their study: periods of extreme drought in particular reduce the amount of carbon absorbed by forests, meadows and agricultural land significantly.

The project CARBO-Extreme is the first to analyze possible impacts of different climate events on terrestrial ecosystems systematically on a global scale, involving scientists from eight different nations. The project is coordinated by the Max Planck Institute for Biogeochemistry in Jena.